The present invention is directed to automatic liquid dispensing. It principally, but not exclusively, concerns dispensing of viscous materials such as liquid soap.
The conservation and sanitary advantages of automatic flow control in sink and similar installations is well known, and a large percentage of public rest-room facilities have provided automatic faucets and flushers as a result. There is a similar advantage to making liquid-soap dispensing automatic in such installations, but the popularity of doing so has not been great so far.
A significant part of the reason for this is installation difficulty. Installing the liquid-soap dispenser often requires providing extra wiring. A solution to this problem, which is to employ battery-operated systems as is now popular for retrofitting manual faucets to make them automatic, has heretofore involved problems of its own. In particular, the power required to pump liquid soap, which can be fairly viscous, is significant, so battery life would ordinarily be too short to be practical unless the batteries are excessively large.